DE1772511C3 - Process for the production of an electrophotographic recording material - Google Patents

Description

2. The method according to claim 1, characterized in that the photoconductor is poly-N-vinylcarbazole, Poly-N-dimethylaminoacenaphthylene, Poly-N-vinylnitrocarbazole, poly-N-dimethylaminocarbazole, Polyvinyl anthraceri or polyvinyl nitronaphthalene is used.

3. The method according to claim 1, characterized in that a solution of the organic photoconductor is used, which is also used as a sensitizing dye RhodamineG (CI. No. 45150,) Rhodamine B (C. 1. No. 45170), Rhodamine S (C. 1. No. 45050), methylene violet (CI. No. 50205), Ethyl violet (C.I. No. 42600), crystal violet (C I. 4 « No. 42555), methylene blue FZ (C I. No. 52015), methylene blue BH cone. (CI. No. 52015), Victoria blue B (C.I. No. 44045), brilliant green GX CI. No. 42040), malachite green (CI. No. 42000), Auramin G cone. (C.I. No. 41000) or acridine orange NS (C.I. No. 46005) contains.

4. The method according to claim 1, characterized in that a solution of a sensitizer contains orange NS (C I. No. 46005).

5 The method according to claim 1, characterized marked 5 < > indicates that a solution of a sensitizer is used which also contains a polyglycol and / or contains a wetting agent.

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The invention relates to a method for producing an electrophotographic recording material with an organic photoconductor, a sensitizer, optionally a sensitizing dye and optionally further additives, in which a plurality of layers are applied to an electrically conductive layer support. ⁶ p

A wide variety of organic photoconductors, such as poly-N-vinylcarbazole, are already in use known in electrophotographic recording materials; most of these organic photoconductors absorb only UV light with wavelengths in the range around 355 nm. When these photoconductors are used Preparation of practically useful electrophotographic recording materials can be used should, therefore, had to extend their light absorption capacity to the wave range of visible light will. For this purpose it is known to use the spectral sensitivity of this photoconductor Addition of sensitizing dyes and / or sensitizers in the form of an acid, a metal • halides, quinones, ketones and the like. For example, there are already electrophotographic recording materials known to have a sensitizer in their light-sensitive layer next to the photoconductor of the type described and contain a sensitizing dye. Disadvantage of the known electrophotographic recording materials of this type is, however, that they are in use one of, for example, a metal halide such as zinc or tin (IV) chloride, or an acid such as Hydrochloric, sulfuric or phosphoric acid, existing auxiliary sensitizers due to corona discharge are insufficient are highly chargeable and take a long time to reach the saturation potential. Using of dichloroacetic acid, trichloroacetic acid or picric acid or an acid anhydride as a sensitizer shows the electrophotographic recording material obtained a noticeable "light fatigue", d. that is, the chargeability of the photosensitive layer deteriorates if it is before charging is exposed. Finally, there are those produced with such electrophotographic recording materials Image copies are usually heavily obscured, which indicates insufficient charge drainage in the non-image areas is due.

The preparation of the known electrophotographic recording materials of the described The type also presents difficulties because the one used to apply the photosensitive layer Coating solution obtained by dispersing one of the aforementioned sensitizers, e.g. B. a metal halide, and an organic photoconductor was made in a dispersion medium, for a long time, for example, if left to stand for a day tends to gel; an even and lump-free application the coating solutions can thus at best be done with freshly prepared solutions, but that is uneconomical.

It is already known, for example from British patent specification 1 020 506, to apply the photoconductive layer to a layer containing sensitizer in the case of an inorganic photoconductor, namely ZnO, containing electrophotographic recording materials. However, since the aforementioned British patent is concerned with increasing the dark resistance of electrophotographic recording materials and also focuses on inorganic photoconductors, it was not foreseeable that when organic photoconductors and sensitizers are used in separate layers, electrophotographic recording materials can be produced which can be rapidly charged high saturation potential and a low "light fatigue" are distinguished, and in particular the production of the greatest possible extent _k streak-free image copies permit.

The subject of the invention is thus a method of the type described above, which thereby

indicates that there is a solution of at least one sensitizer on the support from an organic carboxylic or sulfonic acid, a metal halide, a boron halide, a Quinone, an aldehyde, a ketone, an alkali metal, alkaline earth metal or ammonium salt inorganic or organic acid, an organic l'iltro compound, a monomeric organic Halogen compound or an inorganic carboxylic acid or a mixture thereof, applied, the applied solution dried, the sensitizer layer with a solution of an organic Coated photoconductor and the recording material dried at elevated temperature will.

A method according to de ^r after the invention produced electrophotographic recording material may be charged by corona discharge rapidly to a sufficiently high potential and an electro-photographic recording materials prepared by known process then has superior photosensitivity. Since the individual layers are produced with separate solutions when carrying out the method according to the invention, there are no problems to be feared which can be attributed to possible gel formation; Furthermore, the solutions used in the production of the individual layers are subject to practically no changes over time and therefore do not need to be freshly prepared on an ongoing basis. It is of particular advantage, however, that the electrophotographic recording materials obtained according to the invention permit the production of fog-free image copies on the image background of which practically no toner adheres.

In the photosensitive photoconductive layer formed when the method according to the invention is carried out, the sensitizer originally applied to the support has diffused uniformly from below through the photosensitive layer. At the same time, the specific electrical resistance of the substrate can also be freely adjusted as desired by the method according to the invention by varying the type and amount of the sensitizer applied to the substrate and the conditions under which the applied sensitizer is dried. The surface of the support is preferably dried at a gradually low temperature of 60 to ICO ^{0 C after the application of the sensitizer solution.} It is believed that the sensitizer applied on the support and coated with a photosensitive coating solution evaporates or sublimates while the photosensitive layer is dried and diffuses uniformly into the photosensitive layer. Consequently, the photosensitive layer has no areas in which the sensitizer would be present in local excess, whereby the electrical resistance of the photosensitive layer is kept in the desired range and, on the other hand, the electrical conductivity of the support is improved.

Sensitizers which can be used in the context of the process according to the invention are, for example, organic Carboxylic acids or organic sulfonic acids, such as monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, Tetrachlorophthalic acid, phenylacetic acid, phthalic acid, 6-methylcoumarinyl acetic acid, malic acid, Benzoic acid, cinnamic acid, 4-toluenesulfonic acid and Benzenesulfonic acid; Metal halides, such as zinc chloride, tin (II) chloride, tin (IV) chloride, aluminum chloride, Nickel chloride, iron (II) chloride, copper (I) chloride, barium chloride, sodium chloride, calcium chloride, lithium chloride, Titanium trichloride, arsenic trichloride, antimony pentachloride, magnesium chloride, magnesium bromide, Potassium bromide, calcium iodide, strontium bromide, chromium bromide, manganese (II) chloride, cerium (IV) chloride,

ίο cerium (111) broride, mercury chloride and arsenic triiodide; Boron halides such as boron trifluoride and boron trichloride; Quinones, such as benzoquinone- (1,4), 2,5-dichlorobenzoquinone, 2,6-dichlorobenzoquinone, chloranilnaphthoquinone- (1,4), 2,3-dichloronaphthoquinone- (1,4), anthraquinone, 2-methylanthraquinone, 1,4-dimethylanthraquinone, 1-chloroanthraquinone, anthraquinone-2-carboxylic acid, 1,5-D / ehIorantbrachinoi, i-chloro-4-nitrcanthraquinone, phenanthrenequinone, acenaphthoquinone, pananthraquinone, Chrysenequinone, thionaphthenquinone,

ao anthraquinone-1,8-disulfonic acid and 2-anilide-1,4-naphthoquinone sulfonic acid; Aldehydes, such as bromal, 4-nitrobenzaldehyde, 2,6-dichlorobenzaldehyde, 2-Älhoxy-1-napnthaldehyd, Oxyindole-3-aldehyde, pyridine-2,6-aldehyde, Biphenyl-4-aldehyde and furfural; Ketones like Acetophenone, benzophenone, 2-acetylnaphthalene, benzylbenzoin, 5-benzoylacenaphthene, 9-acetylanthracene, 9-benzoylanthracene and acetoacetic anilide; Salts, such as zinc nitrate, aluminum nitrate, magnesium nitrate, Manganese nitrate, sodium formate, magnesium acetate. Potassium acetate, potassium tartate, ammonium citrate, iron (III) - sulfate, zirconium acetate, magnesium sulfate and zinc chromate; monomeric organic halogen compounds or nitro compounds such as 1,3-dinitrobenzene, l-nitro-2-dichlorobenzene, trinitrobenzene, l-nitro-3,4-dichlorobenzene, S-chloro ^ -nitroaniline, 2,4,6-trinitroanisole, Picryl chloride, tetrabromoxylene, 1,5-dichloronaphthalene, 1,8-dichloronaphthalene, 1,4-dinitronaphthalene, 1,8-dichloronitronaphthalene, 4-nitrodiphenylbenzoic acid, 4,4'-dinitrodiphenylbenzoic acid, trinitrobenzoic acid, iodoform, picric acid and 4-nitroacenaphthene; Tricyanobenzene and tetracyanoethylene; as well as inorganic acids such as hydrochloric acid, sulfuric acid, Phosphoric acid and nitric acid.

When carrying out the process according to the invention, these sensitizers are dissolved in a solvent, such as water, methanol or toluene, after which the solution obtained is applied to the front side of a layer support.
In the context of the method according to the invention, usable layers are, for example, tracing paper, high quality paper, art paper, baryta paper or polyester films, the back of which has been made electrically conductive in the usual way. If a metal plate is used as the layer support, it can be used as a printing plate after the method according to the invention has been carried out.

In the context of the method according to the invention usable organic photoconductors are, for. B. Connections with heterocyclic and condensed rings, such as poly-N-vinylcarbazole, poly-N-dimethylaminoacenaphthylene, Poly-N-vinylnitrocarbazole, poly-N-dimethylaminocarbazole, Polyvinyl anthracene or polyvinyl nitronaphthalene.

In the context of the process according to the invention usable sensitizing dyes are for example

! wise Rhodamine G (C.I. No. 45150), Rhodämin B

I (C. I. No. 45170), Rhodamine S (C. I. No. 45050), Me-

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ethylene violet (C. 1. No. 50205), ethyl violet (C. I. No. 42600), crystal violet (C. 1. No. 42555), methylene blue FZ (CI. No. 52015), methylene blue BH cone. (CI. No. 52015), Victoria blue B (C I. No. 44045), Brilliant green 'GX (C I. No. 42040), malachite green (C I. No. 42000), auramine G cone. (C I. No. 41000) and Acridine Orange NS (C 1. No. 46005).

When using a sensitizer solution, the additional an electrically conductive material such as polyglycol, a wetting agent and / or a synthetic resin for Coating the support, the electrophotographic properties, in particular the photosensitivity of the electrophotographic recording material ultimately obtained improve.

The following examples are intended to illustrate the process according to the invention in more detail.

example 1

A sensitizer solution prepared by diluting 5 g of concentrated nitric acid with 95 g of methanol was applied evenly to the front of a support made of high quality paper, the back of which had been made electrically conductive, for example using wetting agents, and then applied for 1 minute at a temperature from 80 ⁰ C dried. The front side, which had a sensitizer layer, was then coated by roller coating with a photosensitive coating solution consisting of a 5 percent by weight solution of poly-N-vinylcarbazole in monochlorobenzene in such a way that a 4.0 μm thick layer was formed. The photosensitive layer obtained was dried at a temperature of 115 "C for 5 minutes, while its moisture content was adjusted to 4.0 ° /".

For comparison purposes, electrophotographic recording materials were prepared by the same photosensitive coating solution immediately on the one not bearing a sensitizer layer Front of a corresponding paper backing was applied and dried.

The various electrophotographic recording materials were each negatively charged by means of a corona discharge (6 kV), then exposed through a template placed on top for 3 seconds with a 200-watt tungsten lamp and finally wet-developed. With the electrophotographic recording material produced according to the invention, a high-contrast, true-to-original and largely fog-free copy was obtained. In contrast, the copies obtained with the comparative materials were ^{very blurred and practically unusable due to their low sensitivity (of the 1} comparative materials) to visible light.

Example 2

In the manner described in Example 1, a sensitizer solution was prepared and applied to the front side of a corresponding paper backing. A photosensitive coating solution, which had been obtained by adding 1.4 g of rhodamine B (1% by weight methanolic solution) to 100 g of a 5% by weight solution of poly-N-vinylcarbazole in monochlorobenzene, in a thickness of 4, was applied to the sensitizer layer obtained by roller coating. 5 μπι applied. The photosensitive layer obtained was finally for 5 minutes at a temperature of 120C dried to a moisture content was adjusted to 4.5 ¹ V _n.

For comparison purposes, electrophotographic recording materials were prepared by the same photosensitive coating solution immediately on the one not bearing a sensitizer layer Front of a corresponding paper backing was applied and dried.

ίο The electrophotographic recording materials were negatively charged in the manner described in Example 1 and exposed. Here it turned out that the potential drop of the photosensitive layer of the electrophotographic produced according to the invention

• 5 phic recording material about eight times faster took place than with the reference material.

Example 3

One by dissolving 1 g of picric acid in 99 g

The sensitizer solution obtained in this way in methanol was applied ^{uniformly in an amount of 0.03 g / m 2} to the front side of a substrate consisting of art paper, the rear side of which had previously been made electrically conductive, and ^{dried at a temperature of 60 °} C. for 1 minute. A 5 percent strength by weight solution of poly-N-vinylcarbazole in monochlorobenzene in a thickness of 3 μm was applied to the sensitizer layer obtained. The resulting heat-sensitive layer was finally dried for 2 minutes at a temperature of 120 ° C., with its moisture content being adjusted _{to 4.0 ° / 0.}

For comparison purposes, electrophotographic recording materials were prepared by the same photosensitive coating solution immediately on the one not bearing a sensitizer layer Front of a corresponding paper backing was applied and dried.

A measurement of the photosensitivity of the various electrophotographic recording materials showed that an electrophotographic recording material produced according to the invention was sensitive in practically the entire visible range of the spectrum, while the comparison materials had a maximum sensitivity to light with a wavelength of 355 nm. Further, the various electrophoretic recording materials were charged and exposed in the same manner as in Example 1, and the resulting electrostatic latent images were dry developed. ^{A very clear, fog-free copy 1 was} obtained on the surface of the electrophotographic recording material according to the invention, while the copies on the comparison materials were extremely blurred.

Example 4

A photosensitive coating solution made by adding 1.4 g of a 1.0 weight percent methanolic solution of methylene blue FZ too

100 g of a 5.0 weight percent solution of poly-N-vinylcarbazole in monochlorobenzene has been obtained was, was provided by roller coating on the according to Example 3 with a sensitizer layer Paper applied in a thickness of 4.0 μm. the

^The photosensitive layer obtained in 6S was dried at a temperature of 120 ° C. for 3 minutes while its moisture content was adjusted _{to 4.5 ° / 0.} For comparison purposes, electrophotography

phisclic building materials manufactured by the same photosensitive coating solution immediately on the one not bearing a sensitizer layer Front of a corresponding paper backing was applied and dried.

Now, the electrostatic properties of the obtained electropholographic recording characteristics became determined. The results obtained were graphically presented, with on the ordinate shows the surface potential (in volts) of the photosensitive layers after negative charging by means of 6 kV corona charging and on the Abscissa the time (in seconds) are entered. The graphic representation shows the change in the surface potential of the electrophotographic recording materials after charging is complete Exposure of the photosensitive layer. Curve 1 relates to one produced according to the invention electrophotographic recording material and curve 2 on a conventional method manufactured electrophotographic recording material.

As can be seen from the graph, the electrophotographic After charging is complete, recording materials have a saturation potential that is about twice as high on like the comparative materials; at the same time, however, they show a very rapid drop in potential on exposure, d. H. high sensitivity. The half-life of the potential drop in the inventive produced electrophotographic recording materials is only about one twelfth the half-life of the comparison materials, which is why the former works very well in electrophotographic Have the quick copy process used.

Example 5

A sensitizer solution prepared by dissolving 5 g of zinc chloride in 95 g of methanol was applied equally in an amount of 0.1 g / m "to the front side of a substrate made of matte drawing paper, the back of which had previously been made electrically conductive, and for 1 minute on a Temperature of 70 ^° C. A photosensitive coating solution, which had been prepared by adding 1.0 g of a 1 percent by weight methanolic crystal violet solution to 50 g of a 5.0 percent by weight solution of poly-N-dimethylaminoacenaphthylene in ethylene glycol monomethyl ether, was applied to the sensitizer layer obtained The photosensitive layer obtained was dried at a temperature of 130 ° C. for 3 minutes while its moisture content was adjusted to 4.0 ° / ".

A comparative electrophotographic material was prepared for comparison. Here, on the front side of a layer support described in Example 5, a by mixing 1.4 g of a 5.0 percent by weight methanolic solution of zinc chloride with 50 g of a 5.0 percent by weight solution of poly-N-dimethylaminoacenaphthylene in methyl cellosolve and 1 , 0 g of a 1 percent by weight methanolic solution of crystal violet prepared coating solution applied that 3.6 g of solids per square meter of support surface were deposited. The electrophotographic recording material obtained was then ₀ for 2 minutes, dried to adjust the moisture content to 4.0 ° / at a temperature of 130 ⁰ C.

Both the electrophotographic recording material produced according to the invention and the electrophotographic comparison material produced in the manner described were then negatively charged by means of corona discharge, the saturation potentials (K ₅ ) of both electrophotographic recording materials being measured. Each electrophotographic recording material was then exposed to light by means of a tungsten lamp in order to determine the amount of light in lux · sec required to reduce the surface potential to half, that is, to determine the sensitivity of the respective electrophotographic recording material. The results given in the following table were obtained:

Electrophotographic
Recording material Satiety
potential V,
in volts Sensation
opportunity
(Lux ■ sec) According to the invention
placed
Comparative material 300
280 200
250

It has also been found that the coating solution used in the preparation of the comparative electrophotographic material was very difficult to apply to the substrate after standing for 24 hours and that gel-like precipitates had formed in the coating solution at the end of the coating process. A determination of the electrostatic properties of electrophotographic (comparative) materials produced in this way showed that the surface potential was only 200 V and 343 lux · sec were required to reduce the surface potential to half. In addition, it was found that the comparative electrophotographic material produced in the manner described was unusable in practice .

Example 6

A solution obtained by dissolving 5.0 g of iodoform and 2.5 g of a commercially available wetting agent in 92.5 |

The sensitizer solution prepared in this way in methanol was applied in an amount of 0.5 g / m * to the front of a layer carrier on a polyester film, the back of which had previously been made electrically conductive, and dried for 1 minute at a temperature of 90 ° C . A photosensitive coating solution, which had been obtained by adding 1.0 g of a 1.0 percent by weight methanolic solution of brilliant green to 100 g of a 5.0 percent by weight solution of poly-N-vinylnitrocarbazole in dimethyl formamide, was applied to the resulting sensor layer by rolling coating applied in a thickness of 4.5 μπ) The photosensitive layer obtained was then dried for 2 minutes at a temperature of 120 ° < in the dark, its moisture content being adjusted to a suitable value.

For comparison purposes, electrophotographic recording materials were prepared in the

609628/35

Claims (1)

Patent claims: 1. Method of making an electrophotographic Recording material with an organic photoconductor, a sensitizer, optionally a sensitizing dye and optionally further additives that on an electrically conductive substrate the photoconductor and the sensitizer in adjacent Layers are accommodated and the recording material exposed to elevated temperature is, characterized in that a solution of at least one sensitizer consisting of an organic on the support Carboxylic or sulfonic acid, a metal halide, a boron halide, a quinone, an aldehyde, a ketone, an alkali metal, Alkaline earth metal or ammonium salt of an inorganic or organic acid, an organic nitro compound, a monomeric organic halogen compound or an inorganic carboxylic acid or a mixture of this, applied, the applied solution dried, the sensitizer layer with a Solution of an organic photoconductor coated and the recording material at increased Temperature is dried.